Computing apparatus



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Sept. 18, 1962 R- WERY COMPUTING APPARATUS 6 Sheets-Sheet 5 Filed Nov. 8. 1957 u q fi u u u m k h "Z M iWZ W u a 1 m m u 5 J m m? 5 0.5 w n 5. 6 V i u m Em fi m n N u 5 n u u 6 n .L k L u .11 TL ab delw abcde w a f M 10 wa/ 4 snsrsaz Patented Sept. 18, 1962 3,054,892 COMPUTING APIARATUS Robert W. Mowery, Pittsburgh, Pa., assignor to Westinghouse Air Brake Company, Wilmerding, Pin, a corporation of Pennsylvania Filed Nov. 8, 1957, Ser. No. 695,337 2 Claims. (Cl. 246-182) My invention relates to computers, and in particular to Computing apparatus for deriving a signal in accordance with the rolling resistance of a cut of one or more railway cars on curved track.

In the art of railway car classification, it has long been desired to provide automatic equipment for directing cuts of one or more cars humped into a gravity classification yard to selected storage tracks, while at the same time reducing their initial and relatively high speeds at the hump to safe values for coupling. These relatively high humping speeds have been found necessary in order to ensure that the poorest roller among the cars to be classified will ultimately reach its selected destination in the yard without stalling along the way, which would require an expensive trimming operation. It has been the practice to control the speed of cars in the yard after they have left the hump by car retarders located at selected points along the routes of the cars. In th past, it has been customary to control such retarders manually, or solely in accordance with the weight of each cut, to reduce the speed of each cut to a value selected by the operator in accordance with skill and judgment which could be gained only by years of experience. However, means have now been developed for automatically measuring significant parameters associated with each car as it moves along its route, computing from these parameters the rolling resistance of each car, and controlling the retarders to secure a leaving speed for each car which is a function of its computed rolling resistance. One such system for accomplishing this purpose is disclosed and claimed in the copending application of D. P. Fitzsimmoms and William A. Robison, Serial No. 676,730, filed August 7, 1957, for Automatic Control System for Railway Classification Yards, and assigned to the assignee of the present application.

In constructing an automatic control system of the kind shown in the above-mentioned copending application, it has been found necessary to provide means for measuring the rolling resistance of each car on curved portions of track in its route as well as on straight or tangent portions, since it has been found that there is no convenient correlation between the tangent and curved track rolling resistance values. It is, therefore, desirable to provide means for automatically computing the rolling resistance of a cut of one or more cars on a curved stretch of classification yard track. It is an object of my invention to provide such computing means, comprising means for measuring significant parameters affecting the rolling resistance of a cut of one or more cars on curved track, and means for computing the curved track rolling resistance for the cut from the measured values of said parameters.

It has been found that for cuts of railway cars of substantial length, the rolling resistance on curved track may be approximated to a sufiicient degree of accuracy by an average value selected in accordance with the average weight per axles of the cut. Accordingly, it is a further object of my invention to provide, in computing apparatus of the class described, means for automatically supplying an average value of curved track rolling resistance in accordance with the axle loading of a cut of one or more cars when the length of the cut is in excess of a predetermined length.

It is a further object of my invention to provide a computer for evaluating a function of a plurality of independent variables comprising means for storing selected values of said function corresponding to a preselected plurality of values of said independent variables, means for measuring said variables and registering in accordance with said measurements the closest one of each of said predetermined values of each of said independent variables, and means for supplying an output in accordance with the stored value of said function corresponding to said registered values.

Other objects and further advantages of my invention will become apparent to those skilled in the art as the description proceeds.

In practicing my invention, which is intended to be applied to a classification yard of the type having a master retarder and one or more group retarders, I provide means for controlling the speed of cuts leaving the master retarder to a value selected from a group of predetermined values in accordance with the axle loading of the cut. I further provide means for checking that the selected master retarder leaving speed has been attained. These means may be constructed and arranged as shown in the abovementioned copending application of Fitzsimmons and Robison. I further provide, in each stretch of track of varying curvature between the master retarder and the group retarders, means located in approach to each group retarder for measuring the length of each cut and registering this length according as it falls within one of a predetermined plurality of length ranges. I further provide means for measuring the speed or" each cut in approach to the group retarder in its route. In addition, I provide means for storing a plurality of values of two functions, to be defined, in accordance with selected values of weight, cut length and the position of an operating lever for adjusting the overall characteristics of the yard, and means for selecting pairs of values of these functions in accordance with the measured weight and cut length and the position of the lever. Means are also provided for multiplying the values of one of these functions by the measured velocity of the cut approaching the group retarder, and for summing the value so obtained with the value of the other selected function in order to obtain the curved track rolling resistance of the out. To provide for the case in which the length of the cut exceeds a predetermined value above which an average value may safely be employed, I provide means for selecting such an average value in accordance with the measured axle loading of each cut, and supplying this value when the cut length is in excess of the predetermined length. To provide for the possibility that the cut may not reach its predetermined exit velocity when released by the master retarder, I also provide means for supplying the average value when this condition arises.

I shall first describe in detail one embodiment of my invention, and shall then point out the novel features thereof in claims.

In the drawings, FIGS. 1 through 5, arranged as shown in FIG. 6, comprise a schematic wiring diagram of one embodiment of my invention,

FIG. 6 is a diagram showing the manner in which FIGS. 1 through 5 should be arranged to disclose the illustrated embodiment of my invention, and

FIG. 7 is a graph of rolling resistance as a function of velocity employed to illustrate the theory underlying my invention.

Referring now to the drawings, for simplicity I have illustrated my invention as applied to one pair of routes in a classification yard having eight storage tracks of which tracks IT and 2T are shown. However, it will beapparcut to those skilled in the art that in practice many classification yards have sixty or more such storage tracks, and the application of my invention to such yards will be obvious from the description. My invention is adapted to be employed in combination with other components of a system such as the system disclosed and claimed in the above-mentioned copending application of Fitzsimmons and Robison. Since most of the apparatus required for such a system is unnecessary to the understanding of my invention, I have illustrated only those parts of the apparatus shown in the copendiug application which are directly involved in the operation of the illustrated embodiment of my invention, and where convenient to do so, I have illustrated such related apparatus chiefly by block diagrams. However, these blocked-in portions will readily be identified with corresponding portions shown in detail in the copending application as the description proceeds.

In the drawings, most of the apparatus is operated by a conventional 24 volt DC. power supply, not shown, having positive and negative terminals indicated by arrows and respectively designated B and N. Additional power supplies are shown by battery symbols referenced to a common potential indicated by the ground symbol.

Before describing the illustrated embodiment of my invention in further detail, an explanation of the theory underlying its operation will be given. Referring to FIGS. 1 and 2, the stretch of track between the exit end of the master retarder, point a in FIG. 1, and the entrance end of the group retarder, point 2 in FIG. 2, represents a typical route segment which, in practice, would be curved, though for reasons of convenience it is shown in the drawings as a straight line. In practice, it is preferred to lay out the yard so that the curvature of this portion of each route is generally similar to the curvature of the portion of the route from the exit end of the group retarder to the point of tangency of the body track in the route.

The distance D (FIGS. 1 and 2) between the exit end of the master retarder and the entrance end of the group retarder is a fixed constant for each route. However, a cut is not free-rolling over all of this distance, since it has advanced into the stretch by a distance CL equal to its length before it is released from the master retarder. Accordingly, the free-rolling distance travelled by each cut is given by D =D -CL If the velocity (at point 1) at which the cut becomes free-rolling is V mph, the velocity at the entrance end of the group retarder is V mph, the free-rolling distance is D feet, and the stretch has a constant grade G percent, it can be shown that Where R is the rolling resistance of the cut in lb./ ton. If the rolling resistance were Zero, it can be shown from equation (2) that Where V is the velocity in m.p.h. that a car with no rolling resistance would have at point 2. Rewriting Equation 2,

equation of the form Where 0 and k are constants determined by the best fit of a straight line on a curve of V versus R plotted from Equation 2. FIG. 7 illustrates a practical example or" the method employed. In FIG. 7, the curved lines correspond to values of V of 7,8 and 9 mph, for a free-rolling distance D of 360 feet on a track having a grade of 1.29%. The straight lines are formed in this case by drawing a line between points on the curves at R :5 and R :15 lb./ton. It can be seen that these lines approximate the curves very well up to about 20 lb./ ton, which covers the range of practical interest. The constants c and k in Equation 6 can be determined analytically, or they can be determined directly from FIG. '7 by well known graphical methods, using values of V corresponding to the selected values of V from Equation 3, and the selected value of D Equation 6 may be combined with Equations 1 and 3 to give gtia avz) 7 R M 3.34 1. 64.4 1),,2

3.34 +6 W2 Rm Since V is determined in the illustrated embodiment of the invention, in dependence on the weight of the cut and the position of a lever FNS, to be described, while 0 and k are determined by V D 2 and CL, for a given measuring stretch a2 we can define In practice, I- find it sufiicient to divide weight into two categories, light and heavy, medium weight cuts being treated as heavy, to divide cut lengths into four categories, and to provide three operating positions for the FNS lever. Therefore, only twenty-four solutions for u and v are required in order to compute R 2 for any value of V As will appear, these solutions are pre-computed and stored, and proper values are then selected for a particular case in accordance with the values of W, FNS and CL for the cut in question.

One embodiment of the apparatus which I provide for applying the theory developed to the measurement of curved track rolling resistance in an actual yard will now be described. Referring to FIGS. 1 through 3, the two illustrated routes in the portion of the yard shown comprise a common portion including a hump, an approach track section AT, first and second master retarder track sections MRllT and MRZT, a stretch of track comprising detector track sections ll-ST and 1-4T with the associated switches W and 1-4W in their normal positions, four measuring track sections CL1T, CLZT, CLST and CL4T, and a group retarder comprising two track section l2GRlT and l-ZGRZT. The first route then continues over detector track section 12T with switch 12W in its normal position and includes storage track IT, and the second route extends over detector track section 12T with switch LEW in its reverse position and includes storage track 2T. All of these track sections are limited by conventional insulated joints as schematically indicated, and may be provided with conventional track circuits as described in the above mentioned application of Fitzsimmons and Robison.

A weight rail contactor WRC has its contacts located just inside the entrance of the master retarder section MRlT as schematically shown in FIG. 1. Suitable apparatus for this purpose is shown in somewhat more detail in the abovementioned copending application of Fitzsimmons and Robison. The output of contactor WRC is applied to weight coding, storage and transfer circuits 1 terminating in a pair of weight repeater storage relays l-ZALP and l-ZAl-IP as schematically shown. This apparatus is shown in detail in the copending application of Fitzsimmons and Robison. Referring to FIG. 43 of the copending application, relays AH]? and ALP in the A bank of the 12 phantom storage location correspond to relays 1-2ALP and l-2AHP in FIG. 1 of the present application. Since the details of the circuits for controlling these relays form no part of my present invention, they are not shown.

The two sections of the master retarder are provided with master retarder speed measuring and control apparatus 2, the details of which are shown in the abovementioned copending application of Fitzsimmons and Robison. It is sufficient for the purposes of illustrating my invention to point out that this apparatus functions in accordance with the value of weight supplied from the weight coding, storage and transfer circuits and the setting of an FNS lever, :as schematically indicated, to control the speed of each cut leaving the master retarder to a value V selected in accordance with the weight and the FN S lever setting.

As fully described in the above-mentioned copending application, the master retarder leaving speed V and the actual speed V of each out are supplied to correct leaving velocity check, storage and transfer circuit 3 here schematically shown in block form. Referring to FIG. 54 of the above-mentioned copending application, relay AlV corresponds to relay 12AIV as shown in FIG. 1 of the present application. Since the details of the circuits for controlling this relay form no part of my invention, they are not shown.

The distance D 2 from the exit end of the master retarder to the entrance end of the group retarder is indicated in FIGS. 1 and 2. In order to measure the freerolling distance D 2 for each cut, the cut length CL must be determined. For this purpose, four track circuits CLllT, CLZT, CLBT and CLdT are provided, together with a cut length measuring circuit 4, as shown schematically in FIG. 2. The details of the construction and the mode of operation of this apparatus are more fully described in the above-mentioned copending application of Fitzsimmons and Robison, and are also described and claimed in the copending application of Joseph M. Berill, Serial No. 696,406, filed November 14, 1957, for Cut Length Detector, now U.S. Patent 2,976,- 401, granted March 21, 1961, and assigned to the assignee of the present application. Briefly, track sections CLlT and CL4T may be, for example, 58 feet in length, and track sections CLZT and CL3T may be 29 feet in length. Repeater relays CLlTP, CLZTP, CL3TP and CL4TP are associated with their respective track sections in a conventional manner, as indicated schematically in FIG. 2, and are energized or deenergized according as the associated track sections are occupied or unoccupied. These relays control circuits which operate as described in the previously mentioned copending applications in conjunction with other relays, not shown, to energize one or more of relays CLA, CLB and CLC accordingly as the cut length falls within one of four predetermined ranges.

As described in the above-mentioned application of Fitzsimmons and Robison, if the length of the cut is between 0 and 29 feet, relays CLA and CLB will be energized. If the length of the cut is between 29 and 58 feet all three relays will be energized. If the length of the cut is between 58 and 87 feet, relays CLB and CLC will be energized. If the length of the cut is between 87 and 116 feet, only relay CLC will be energized. If the length of the cut is greater than 116 feet, none of the relays will be energized. The manner in which these relays are employed in the operation of this: embodiment of my invention will be described below.

If the cut length measuring circuits, inst described, are not operating properly, or if the length of the cut is greater than the predetermined length above which an average value of rolling resistance can safely be supplied, it is desired to register this information so that appropriate steps can be taken in the computer. For this purpose, relay RTA, shown in FIG. 2, is employed. Relay RTA has a first pickup circuit extending from terminal B of the battery over the front point of contact 0 of relay CLA and back contact b of relay CLB, through the winding of relay ETA, and thence to terminal N of the battery. Relay ETA has a second pickup circuit extending from terminal B of the battery over the back point of contact 0 of relay CLA, back contact 0 of relay CLC, and through the winding of the relay to terminal N of the battery. As noted above, the four combinations of energized relays which are employed for measuring are CLA and CLB; CLA, CLB and CLC; CLB and CLC; and CLC alone. Of the remaining possible combinations, there are two in which relay CLA is energized and relay CLB is released, and the circuit for relay RTA will be completed in these cases over its first previously traced pickup circuit. In the remaining two possible combinations, both of relays CLA and CLC are deenergized, and relay RTA will be energized in these cases over its second previously traced pickup circuit. Accordingly, relay RTA will be energized and will hold up its contact a when and only when no out length Within the measurable range is being registered.

The two sections of the group retarder, FIG. 3, are controlled by group retarder speed measuring and controlling apparatus 5, which may be of the type shown and described in the above mentioned copending application of Fitzsirnmons and Robiso-n. As explained in that application, these circuits include a radar velocity meter 6 having one terminal b connected to an. antenna 7 located adjacent the exit end of track section l-2GR1T and facing toward the hump as shown. Output terminal a: of radar velocity meter 6 suppli s a voltage with respect to ground which is proportional to the speed of cars approaching and occupying section l-ZGRFLT. The utility of this output will be described below.

The computing apparatus employed in this embodiment of my invention comprises a relay CLVP (FIG. 1), which checks that the length of the cut is under 116 feet and that the cut has left the master retarder at the preselected velocity V as will be described; a test compute relay TC (FIG. 1), to be described; two weight storage relays RLP and RH? (FIG. 1) six computer ratio panels, lCRP through soar (FIGS. 2, 3, 4- and 5), a summing amplifier 3 (FIG. 1), and additional elements which will be described.

Relay CLVP has a pickup circuit extending from terminal B of the battery over front contact a of relay l-ZAIV (FIG. 1), lead 9, front contact a of relay CIATP, which is picked up when track section CL iT is occupied, lead 16, back contact a of relay RTA, lead 11, and through the winding of relay CLVP to terminal N of the battery. As more fully described in the abovementioned copending application of Fitzsimmons and Robison, relay 1ZAiV is picked up when a cut has left the master retarder at its correct selected leaving velocity V and has occupied track section CL i-T. Accordingly, relay CLVP will be picked up when section CLET is occupied only if the associated cut has left the master retarder at the correct selected velocity and relays CLA, CLB and CLC have registered a length in one of the four measurable classifications as indicated by the dcenergized condition of relay RTA. The energized condition of relay CLVP thus indicates that the computer can proceed to supply an actual solution of R rather than an average value, whereas the deenergized condition of relay CLVP directs the computer to supply an average value of R The control and function of relay TC are more fully described in the above-mentioned copending application of Fitzsimmons and Robison. Briefly, it is energized when section CL4T is not occupied by a cut, and it is deenergized when section CLdT is occupied. For this purpose, it has a pickup circuit extending from terminal B of the battery over back contact b of relay CLdTF in FIG. 2, lead 12, and through the winding of relay TC to terminal N of the battery. As described in the application of Fitzsimmons and Robison above referred to, during the time that relay TC is energized the computing apparatus of the system as a whole is supplied with simulated input conditions to check whether it is operating properly. For this purpose, the apparatus of my invention supplies a simulated value of R as will be described below.

Relays RL? and RH? in FIG. 1 repeat the weight information stored in weight coding, storage and transfer circuits 1 when track section CL4T is occupied. Relay RLP has a pickup circuit extending from terminal B of the battery over front contact a of relay 12ALP, lead 13, front contact (I of relay CLdTP, lead 14, and through the winding of relay RLP to terminal N of the battery. Relay RH? has a pickup circuit extending from terminal B of the battery over front contact a of relay 1-2AHP, lead 15, front contact of relay CL iTP, lead 96, and through the Winding of relay RHP to terminal N of the battery. As described in the copending application of Fitzsimrnons and Robison, relays 1-2ALP and 1-2AHP are energized in a combination depending on the axle loading of each cut when section CL iT is occupied. For light cuts, with cars weighing between l6 and 32 tons, only relay 1-2ALP is energized; for medium weight cuts of cars weighing between 32 and 50 tons, both relays 1-2ALP and l-ZAHP are picked up; and for heavy cuts, comprising cars weighing over 50 tons, only relay 12AHP will be picked up. Relays RLP and RHP will repeat these indications over the circuits just described during the occupancy of section CL'dT.

The FNS lever has contacts schematically shown in FIG. 1 corresponding to fast, slow and normal operating conditions in the yard as more fully described in the copending application of Fitzsimmons and Robison. Contact F is connected to the heel of contact a of relay CLVP, contact N is connected to the heel of contact 12 of relay CLVP, and contact S is connected to the heel of contact 0 of relay CLVP, as shown. The movable element of the lever is electrically connected to terminal B of the battery as schematically indicated. With relay CLVP energized, one of leads 16, 17 and 13 will accordingly be energized in accordance with the position of lever FNS. The energized one of leads 16, 17 and 18 then selects a pair of panels from the six ratio computer panels lCRP through 6CRP as will be described.

Each of panels R? through 6CRP is of identical construction, and, therefore, only panels llCRP (FIGS. 2 and 4) and 4CRP (FIGS. 3 and 5) will be described in detail. Panel ICRP includes relays L1, M1, 1CL1 and ICLZ (FIG. 2) and eight potentiometers 19, 20, 21, 22, 23, 24, and 26 (FIGS. 2 and 4). Panel 4CRP includes as relays L4, M4, 4CL1 and i-CLZ (FIG. 3), and eight Potentiometers 27, 28, 29, 30, 31, 32, 33 and 34 (FIGS. 3 and 5).

Relay L1 in panel IlCRP has a pickup circuit which extends from terminal B of the battery over the F contact of the FNS lever (FIG. 1), front contact a of relay CLVP, lead 16, lead 36, terminal a of panel lCRP, and through the winding of relay L1 to terminal N of the battery. It will be noted that when this circuit is completed, a parallel circuit from lead 16 over lead 35 is completed to energize relay L4 in panel dCRP (FIG. 3). Similarly, panels 2CRP and SCRP may be selected together by the energization of relays L2 and L5 with lever FNS in its N position. The circuit for this purpose extends from terminal B of the battery over terminal N of the lever FNS in its N position and front contact I) of relay CLVP to lead 17, and thence over a first path including lead St), terminal a of panel ZCRF, and the winding of relay L2 to terminal N of the battery, and over a second path including lead 79, terminal a of panel SCRP, and through the winding of relay L5 to terminal N of the battery. With lever FNS in its S position, panels ECRP and 6CRP are selected together by the energization of relays L3 and L6. The circuits for this purpose extend from terminal B of the battery over terminal S of the ENS lever in its S position and front contact 0 of relay CLVP to lead 18, and thence over a first path including lead 99, terminal a of panel SCRP and the winding of relay L3 to terminal N of the battery, and over a second path including lead 81, terminal a of panel GCRP, and the winding of relay L6 to terminal N of the battery. As will appear, the remaining relays in panels lCRP through 6CRP are controlled over contacts of the associated L relays. In the following description, where necessary for illustration, it will be assumed that panels ECRP and 4CRP have been selected. However, it will be apparent that if other pairs of panels were selected, similar circuits would be completed.

Relay M1 (FIG. 2) has a pickup circuit extending from terminal B of the battery over front contact a of relay RLP (FIG. 1), back contact a of relay RHP, lead 37, lead 38, lead 39, terminal 0 of panel 1CRP, front contact [2 of relay L1, and through the winding of relay M1 to terminal N of the battery. This relay is accordingly picked up it a light cut is under control and if panel ICRP has been selected. It will be noted that parallel circuits extend from lead 38 over leads 40, 41 and 42 to relays M2 and MS of panels ZCRP and 3CRP, and over leads 43, 4 45, 46 and 47 to relays M4, M5 and M6, respectively, in panels 4CRP, SCRP and cCRP, respectively. With the exception of relay M4 in panel 4CRP all of these circuits will be interrupted at the open front points of the contacts of the L relays in the panels, if panel 1CRP has been selected. However, relay M4 will be picked up if relay M1 is picked up since panels 1CRP and iCRP are used together.

Relay 1CL1 (FIG. 2) has a pickup circuit extending from terminal B of the battery over front contact b of relay CLC (FIG. 2), back contact b of relay CLA, lead 48, lead 50, lead 51, terminal d of panel 1CRP, front contact c of relay L1, and through the winding of relay 1CL1 to terminal N of the battery. This relay is accordingly picked up if the cut length is between 58 and 116 feet. It will be noted that the GL1 relays in panels ZCRP and 3CRP will be supplied by the circuit just traced from lead 50 over lead 52 and leads 53 and 5- respectively, but

over front contact d of relay GLG (FIG. 2), and thence over alternate paths, the first including front contact c of relay GLB and the front point of contact d of relay CLA, and the second including back contact at of relay GLB and the back point of contact d of relay CLA, and thence over a common path over the heel of contact d of relay CLA to lead 59, front lead 59 over a first lead 60 which supplies the GL2 relays of panels IGRP, ZGRP and SGRP, by connections to their 2 terminals over leads 61, 62 and 63, and 62 and 64, respectively. The GL2 relays of panels tGRP, 5GRP and 6GRP are supplied from lead 59 over lead 65 (FIG. 2), and thence to their respective terminals 6 over leads 66, 67 and 68, and 67 and 69, respectively. In each of the panels, and for example in panel lGRP, if terminal e of the panel is energized from terminal B of the battery, the circuit may be completed over the front contact of the L relay, and for example over front contact a of relay L1, and through the winding of the GL2 relay such as 1GL2 to terminal N of the battery.

Accordingly, if relays L1 and L4 are picked up to select panels lGRP and tGRP, relays 2GL2 and dCLZ will be energized if the cut length is either between 29 and 58 feet or between 87 and 116 feet. The GL1 and GL2 relays in combination, therefore, give all of the information stored in relays CLA, GLB and CLC, since with neither of the GL1 nor GL2 relays up, the cut length must be below 29 feet, with only relay GL1 up, the length must be between 58 and 87 feet, with only relay GL2 up, the length must be between 29 and 58 feet, and with both of relays GL1 and GL2 up, the length must be between 87 and 116 feet.

Referring now specifically to panel ICRP, one of potentiometers 19 through 26 will be selected in accordance with the energized or deenergized condition of relays Ml, IGLl and 1GL2. These potentiometers are set to represent values of the function v to be multiplied by the velocity V Referring now to FIG. 3, the output velocity V from velocity meter 6 is supplied from output terminal a over lead 70, front contact 2 of relay GL iTP, lead 71, and thence over lead 72 to input terminal of panel llGRP, over leads 73 and 74, to input terminal b of panel 2GRP, and over lead 75 to input terminal b of panel 3GRP. Since the circuit from this point on is the same in each of the panels, attention will again be confined to panel IGRP, in which the circuit is continued from terminal b to the heel of contact a of relay L1.

When relay L1 is energized, potentiometer 19 may be supplied over the front points of contacts a of each of relays M1, llGLl and lGLZ. Potentioineter 26 may be supplied from front contact a of relay L1 over the front point of contact a of relay M1, the front point of contact a of relay iGLl, and the back point of contact a of relay 1GL2. The rest of the potentiometers will be selected over similar circuits. Specifically, if relay M1 is energized for a light cut, one of potentiometers 19 through 22 will be selected, and if relay iGLl is picked up, one of potentiometers 19 and 29 will be selected depending on whether or not relay 1GL2 is picked up. If relay ilGLl is deenergized, one of potentiometers 21 and 22 is selected in accordance with the energized or deenergized condition of relay iGLZ. If relay M1 is released for a heavy or medium cut, one of potentiometers 23 through 26 is selected, one of potentiometers 23 and 24 being selected if relay 1GL1 is energized in accordance with the energized or deenergized condition of relay 1GL2 and one of potentiometers 25 and 26 being selected if relay 1GL1 is released in accordance with the energized or deenergized condition of relay 1GL2.

The one of potentiometers 19 through 26 which has been energized over the contacts of relays M1, lGLl and 1CL2 has its wiper connected to output terminal 1 of panel lGRP over a combination of contacts similar to the combination over which it was energized. The purpose of thus disconnecting the non-selected potentiometers at both sides is to prevent them from loading the output circuit. It is believed that the arrangement of contacts for this purpose is sufliciently obvious from the drawings not to require a detailed explanation for each potentiometer. As an example, however, if relay M1 is picked up, relay lGLl is released and relay 1GL2 is picked up, the measured velocity V appearing at terminal b of panel EGRP will be connected to the resistive element of potentiometer 21 over front contact a of relay L1, the front point of contact a of relay M1, the back point of contact a of relay ICU. and the front point of contact 12 of relay 1GL2. The wiper of potentiometer 21 will then be connected to terminal 1 over the front point of contact d of relay M1, the back point of contact c of relay lGLl and the front point of contact e of relay 1GL2.

As is well known in the art, a voltage analogous to the product of two values may be obtained by applying a voltage proportional to one of the values across a potentiometer having a wiper adjusted above ground by an amount proportional to the other value, the voltage then appearing between the wiper and ground being proportional to the product of the two values. In the present case, a voltage proportional to the velocity V of the cut approaching the group retarder is applied across the resistive element of the selected potentiometer, and the wiper is initially adjusted in the calibration of the apparatus to introduce one value of the function v. Eight values of v are thus available in each of panels iGRP, ZGRP and 3CRP, each set of eight being calculated on the basis of a different position of the ENS lever, and the values within each set being computed in accordance With the eight possible combinations of weight and cut length represented by the M, GLll and GL2 relays.

Panels 4GRP, SGRP and 6GRP are employed to select the proper coeflicient function u in Equation 10 for the selected value of V the leaving velocity from the master retarder. Since the apparatus will not function in a completely automatic manner unless the correct leaving velocity V has been secured, and since the value of V is initially selected on the basis of the FNS lever position and the weight of the cut in the categories of light and heavy, it is suflicient to employ a fixed reference voltage to represent V which is modified in accordance with weight and FNS position. This reference voltage is supplied by a suitable source of voltage such as a battery 76 (FIG. 1) wihich has its positive terminal grounded, as shown, and has its negative terminal connected through resistance 77 and lead 78 to terminals b of panels t-GRP, SCRP and 6GRP.

One of panels AtGRP, SGRP and 6GRP is selected by the position of the FNS lever as previously described. With one of relays L4 and L6 picked up, one of relays M4 through M6 may be energized over the previously traced circuitincluding front contact a of relay RLP, back contact a of relay RHP, leads 37 and 43, and thence to terminal 0 of the selected panel, over front contact 11 of the selected L relay, and through the winding of the selected M relay to terminal N of the battery. In the same manner, the GL1 and GL2 relays in the selected panel may be picked up over front contacts c and d of the selected L relay in accordance with the combined condition of relays CLA, GLB and GLG.

Each of panels dGRP, SGRP and 6GRP includes eight potentiometers such as potentiometers 27, 28, 29, 30, 31, 32, 33 and 34 shown for panel 4GRP. Each of these potentiometers has a wiper adjusted to provide an output voltage in response to the applied voltage from battery 76 which is proportional to a particular value of u in Equation 10. Since the applied voltage from battery 76 is negative, this output voltage will be negative with respect to ground. The reason for this polarity will be explained below.

The selected one of potentiometers 27 through 34 in panel 4GRP has its resistive element connected across battery 76, which is applied to terminal 12 of panel 4CRP, and its output wiper connected to terminal 1 of panel 4CRP, over a combination of contacts of relays M4, 4CL1 and 4CL2. That is, if relay M4 is picked up, one of otentiometers 27 through 369 is selected, and if it is released, one of otentiometers 31 through 34 is selected. If relay 4CL1 is picked up, one of potentiometers 27 and 28 will be selected if relay M4 is picked up and one of potentiometers 31 and 32 will be selected it relay M4 is released. If relay 4CL1 is released, one of potentiometers 29 and 30 will be selected if relay M4 is energized and one of otentiometers 33 and 34 will be selected if relay M4 is released. From the pair of potentiometers selected by this process, one is selected by the energized or deenergized condition of relay 4CL2. It is believed unnecessary to trace all of these circuits in detail. For example, however, if relays L4 and M4 are energized and relays CL and M12 are released, the battery potential applied to terminal 11 of panel 4CRP is connected over front contact a of relay L4, the front point of contact a of relay M4, the back point of contact a of relay lCLll, the back point of contact b of relay 4CL2 to one side of the resistive element of potentiometer 30, the other side being connected to ground as shown. The wiper of potentiometer 30 is then connected to output terminal f of panel 40R over the front point of contact a of relay M4, the back point of contact d of relay 4CL1 and the back point of contact e of relay dCLZ. The corresponding circuits in panels SCRP and fiCRP are identical with those just described for panel 4CRP.

The selected one of panels lCRP through 3CRP will have an output voltage proportional to vV appearing between its output terminal 1 and ground, while terminals 1 of the remaining panels will be open circuited internally at the open front point of contact a of the respective L relays. The terminals f of these panels are connected together and are connected over lead 32 and through a summing resistor 33 to input terminal a of a summing amplitier 8 (FIG. 1) which has its other input terminal b grounded as shown. Similarly, one of output terminals of panels 4CRP through 6CRP will have an output with respect to ground which is proportional to u. These terminals 1 are connected together and are connected over lead 84 and through a summing resistor 85 to input terminal a of amplifier 8. Amplifier 8 may be provided with a suitable feed-back resistor 36 and may be of conventional construction which need not be described in further detail.

Due to the inversion in amplifier 8, the output voltage at terminal c of the amplifier with respect to grounded terminal d is proportional to u-vV which is equal to R 2 from Equation 10. This value is made available to the group retarder leaving speed computer 87 (shown schematically in FIG. 3 and fully described in the abovementioned copending application of Fitzsimmons and Robison) over a circuit extending from terminal of amplifier 8 over the front point of contact e of relay CLVP, the back point of contact a of relay TC, and lead 89.

If relay CLVP is released when track section CL4T is occupied, either the out has not left the master retarder with the correct leaving velocity or it is too long to be measured, and hence long enough to warrant the use of an average value of rolling resistance. In either case, an average value of R 2 is supplied. This value is modi fied by the weight of the cut in order to more nearly represent the actual conditions. For this purpose, as shown in FIG. 1, three potentiometers M, L and H are provided, each having a wiper which is initially adjusted in the calibration of the yard to give the best average value of R 2 for the corresponding weight category. Potentiometer M may have one end of its resistive element connected to the negative terminal of battery 7 6 through a suitable resistor 88, over back contact d of relay CLVP, the front point of contact b of relay RLP, and the front point of contact b of relay RHP, the other end being connected to ground 12 as shown. The wiper of potentiometer M may be connected to output lead 89 over the front point of contact 0 of relay RLP, the front point of contact d of relay RHP, the back point of contact 2 of relay CLVP, and the back point of contact a of relay TC.

The resistive element of potentiometer L may have one end connected to the negative terminal of battery 76 through resistor 88, back contact at of relay CLVP, the front point of contact b of relay KL? and the back point of contact b of relay RHP, the other end being connected to ground as shown. The wiper of potentiometer L may be connected to output lead 89 over the front point of contact a of relay RLP, the back point of contact d of relay RHP, the back point of contact e of relay CLVP and the back point of contact a of relay TC.

Potentiometer H may have one end of its resistive element connected to the negative terminal of battery '76 through resistor 88, back contact at of relay CLVP, the back point of contact b of relay RLP and the front point of contact c of relay RHP, the other side being connected to ground as shown. The wiper of potentiometer H may be connected to output lead 39 over the back point of contact 0 of relay RLP, the front point of contact a of relay RHP, the back point of contact e of relay CLVP and the back point of contact a of relay TC.

During the time that the computer is not solving for a value R 2 for a particular cut, it is desired to provide a test problem for solution to test the operation of the computer. For this purpose, the computing apparatus of my invention merely provides a single value to the group retarder leaving speed computer 87. This value is provided by connecting one end of resistor 90 to the negative terminal of battery 76 and the other end to one end of a resistor 91, which has its opposite end grounded as shown, thus forming a fixed voltage divider. The voltage at the junction of resistors 90 and 91 may be applied to output lead 89 over the front point of contact a of relay TC, which is picked up when track section CL4T is unoccupied.

It will appear from the above description that with section CL4T occupied by a cut of measurable length which has left the master retarder at the selected leaving velocity V the value R 2 is computed in a selected pair of panels lCRP through GCRP and summing amplifier 8, and an output proportional to R 2 is applied to output lead 89 and thence to group retarder leaving speed computer 87 over the front point of contact e of relay CLVP and the back point of contact a of relay TC. If the cut is too long, or if its leaving velocity is not correct, an average value of R 2 will be supplied to one of potentiometers M, L and H over the back point of contact e of relay CLVP and the back point of contact a of relay TC. When the computer is in a standby condition, with track section CL4T unoccupied, a test value of R 2 will be supplied from the potential divider comprising resistors 96 and 91 over the front point of contact a of relay TC.

In order to illustrate the operation of this embodiment of my invention, a numerical example will be given. Assume that the length D :456 feet. Further, assume that a cut 96 feet long is to be classified, and that the average weight of the cars in the cut is 56 tons, corresponding to an axle loading of 14 tons, which would be classified as heavy. With the FNS lever in the F position, the leaving speed V selected for the cut would, in one practical embodiment, be 12.0 m.p.h.; however, to simplify the illustration with the apparatus in the condition shown, a value of 8 m.p.h. will be assumed for V If the grade G 2 of the curved measuring stretch is 1.29%, since D =456-96=360, the middle curve of FIG. 7 may be used to compute c and k. From Equation 3, with the values given, V *=l4.2 m.p.h. Equafrom set (b) and Equation 11, and using the above value for c,

As shown above, D =D CL=36O feet, and from Equations 8 and 9,

For reasons which will appear, potentiometer 23 in panel lCRP and potentiometer 31 in panel 4CRP will be selected. For simplicity, assume that it is desired to provide an output voltage of one volt per 1b./ton rolling resistance, and that the output of velocity meter 6 appearing between terminal a and ground is ten volts per m.p.h. In accordance with the above values, potentiometer 23 will be adjusted with its wiper of the total resistance value above ground, so that its output will be 4.46 V volts per m.p.h. Assuming that the potential of battery 76 is such that a voltage of l00 volts is applied across the resistive element of the selected potentiometer, the wiper of potentiometer 31 will be adjusted of the total resistance value above ground, to supply 64.5 volts when connected across the battery.

With the apparatus initially adjusted as just described, let it now be assumed that the cut under consideration is released from the hump with an initial speed of 15 mph.

For the complete sequence of operations carried out by a system of the kind of which the apparatus of my invention is intended to be employed, reference should be made to the above mentioned copending application of Fitzsimmons and Robison. Here only those aspects of such operation which afiect the operation of my invention will be described. After the cut rolls down from the hump and has traversed track section AT, it enters section MRIT and begins to actuate weigh rail contactor WRC. The weight coding, storage and transfer circuits now begin to function in the manner described in the copending application, but at this time the 70 weight registration will be maintained by preliminary means within these circuits, not shown. These circuits operate in the manner described in the copending application, in conjunction with the setting of lever FNS, to select a master retarder leaving speed for the cut. 75

In the example under consideration, since the FNS lever is in the F position, and the assumed weight of the cars of the cut is 56 tons, the speed selected, as pointed out in the copending application, might be 12 miles per hour in practice. However, as noted above, for purposes of illustration, it will be assumed that a speed of 8 miles per hour has been selected. It will be assumed that as the front of the cut reaches point 1 in FIG. 1, which in this case is 96 feet from the exit end of the master retarder, it has reached the desired speed of 8 miles per hour and the output signals V and V from the master retarder speed measuring and control circuits 2 are equal. This fact will be registered in the correct leaving velocity, check, storage and transfer circuits 3 in intermediate equipment, not shown. Switches 1-8W and l--W will be positioned normally by switching apparatus, not shown, which is fully described in the copending application. The cut will accordingly occupy detector track sections 18T and 1-4-T in sequence and then sequentially occupy measuring track sections CLiT, CLZT, CLET and CLdT. During this process, cut length measuring circuit 4 will respond to the manner described in the above-mentioned copending applications.

Since the assumed length of the cut is 96 feet, when section CL4-T is occupied, relay CLC will be energized and relays CLA and CLB will be released. Relay CL4TP will be energized at this time. As described in the copending application of Pitzsimrnons and Robison, the computing operation takes place during the occupancy of section CIAT. With relay CL tTP energized, and a heavy cut registered by unit 1, relay ll2ALP in FIG. 1 will be deenergized and relay LZAHP will be energized. Since the correct leaving velocity from the master retarder has been obtained, relay I ZAIV in unit 3 will be energized at this time. Relay RTA (FIG. 2) will be deenergized, since its first traced pickup circuit is interrupted at the open front point of contact 0 of relay CLA, and its second pickup circuit is interrupted at the open back point of contact c of relay CLC.

Relay CLVP will now be picked up over its previously traced circuit including front contact a of relay l2AIV, lead 9, front contact a of relay CL iTP, lead 10, back contact a of relay RTA and lead 11.

The pickup circuit for relay TC will be interrupted at the open back point of contact I) of relay CL4T P. This relay will accordingly remain deenergized.

The pickup circuit for relay RLP will be: interrupted at the open front point of contact a of relay 12RLP. The pickup circuit for relay RHP will be completed over front contact a of relay .l-ZAHP, lead 15, front contact 0 of relay CL4'TP and lead 96. Accordingly, relay RLP will remain deenergized and relay RHP will be picked up.

With the FNS lever in its P position, a circuit will extend from terminal B of the battery over terminal F of the lever, front contact a of relay CLVP, lead 16, and leads 35 and 36 to the a terminals of panels 4CRP and llCRP, respectively. Relays L1 and L4 will accordingly be energized. The corresponding circuits for relays L2, L3, L4, L5 and L6 in the remaining panels Will be open at the disconnected terminals N and S of the lever FNS. These panels will, therefore, play no part in the remaining operation.

With relay RLP released and relay RHP' picked up the previously traced circuits for relays M1 and M4 in panels ILCRP and iCRP will be interrupted at the open front point of contact a of relay RLP and also at the open back point of contact a of relay RHP. Relays M1 and M4- will, therefore, be deenergized during the operation.

With relay CLC picked up and relays CLA and CLB released, a circuit will extend from terminal B of the battery over front contact d of relay CLC, back contact d of relay CLB, back contact d of relay CLA, lead 59, thence over a first path including leads 60 and 61, terminal e of panel ICRP, front contact d of relay L1 and through the winding of relay lCLZ to terminal N of the battery, and from lead 59 over a second path including leads 65 and 66, terminal e of panel lCRP, front contact cl of relay L4, and through the winding of relay 4CL2 to terminal N of the battery. Relays lCLZ and 4CL2 will accordingly be picked up. A second circuit now extends from terminal B of the battery over front contact b of relay CLC, back contact b of relay CLA, lead 18, from lead 48 over a first path including leads and 51, terminal d of panel lCRP, front contact 0 of relay Li, and through the winding of relay lCLl to terminal N of the battery, and from lead 48 over a second path including leads v9 and 55, terminal d of panel KERR front contact 0 of relay L4 and through the winding of relay 4CL1 to terminal N of the battery. Relays lCLl and iCLl will, therefore, be energized.

With the cut occupying section CL4T, it will be in the path of antenna 7 of radar velocity meter 6, which will produce an output voltage at terminal a in accordance with the speed of the cut. Let it be assumed for the purpose of this example that the registered speed is 12 miles per hour. In accordance with the previous assumptions, there will then be a voltage of 120 volts between terminal a and ground. This voltage will be applied over lead 70, front contact 0 of relay CL4T'P, lead 71, lead 72, terminal b of panel iCRP, front contact a of relay L1, the back point of contact a of relay M1, the front point of contact b of relay lCLl, the front point of contact c of relay ICLZ, and through the resistive winding of potentiometer 23 to ground.

With the wiper of potentiometer 26 adjusted as previously described, and 129 volts across the resistive winding of the potentiometer, a voltage of 53.5 volts will appear between the wiper of potentiometer 2.3 and ground. This voltage will be applied over the back point of contact b of relay M1, the front point of contact 0 of relay 1CL1, the front point of contact 2 of relay lCLZ, terminal f of panel lCRP, lead 82, and through summing resistor 83 to input terminal a of summing amplifier 8.

At the same time, the negative terminal of battery 76 will be connected through resistor 77, lead 78, terminal b of panel 4CRP, front contact a of relay L4, back contact a of relay M4, the front point of contact b of relay 4CL1, the front point of contact 0 of relay 4CL2, and through the resistive winding of potentiometer 31 to ground. As previously stated, it is assumed that the potential of battery 76 is such that, taking into consideration the drop across resistor 77, a voltage of l00 volts appears across potentiometer 31. With the potentiometer adjusted as previously described, a voltage of 64.5 volts is now applied from the wiper of potentiometer 31 over the back point of contact b of relay M4, the front point of contact 0 of relay 4CLll, the front point of contact e of relay 4CL2,terminal f of panel dCRP, lead 84, and through summing resistor 85 to input terminal a of summing amplifier 8.

With the inputs just described, a net voltage of -11 volts will be applied to the input of amplifier 8, which, due to the inversion of the amplifier, will cause the potential of output terminal 0 to rise +11 volts above ground terminal d. With the assumptions described, this voltage represents a rolling resistance of 11 pounds per ton. It will be seen from FIG. 7 that this value corresponds to the assumed velocity V of 12 miles per hour.

The output voltage from amplifier 8 is now applied over the front point of contact e of relay CLVP, the back point of contact a of relay TC, and lead 89 to group retarder leaving speed computer 87. This appartus may correspond to V computer 22 in the above-mentioned copending application of Fitzsimmons and Robison. The computer will now operate to compute a leaving speed V from the group retarder in the manner described in the copending application. This signal will be applied to group retarder speed measuring and control apparatus 5, which operates as described in the eepending application to reduce the leaving speed of the cut from the group retarder to the selected leaving speed. The cut will then be routed over switch 1-2W in its normal or reverse position to body track IT or body track 2T, respectively, as desired.

It will next be assumed that a cut of 130' feet in length is to be classified. Since this length is above the measurable range, it will call for an average value of R 2 to be supplied. As examples of typical values which may be employed in practice, for light cars this value may be 11 pounds per ton, for medium cars and value may be 9 pounds per ton, and for heavy cars, the value may be 8 pounds per ton. Potentiometers M, L and H would accordingly be adjusted to provide output voltages of 9, 11 and 8 volts, respectively, in accordance with the other values assumed above. It will be assumed for the purposes of this example that the cut is composed of medium weight cars of, for example, 40 tons average weight. Accordingly, when section CL4T is occupied by the out both relays 12ALP and 1-2AHP in FIG. 1 will be energized.

Since the length of the cut is above the measurable range, as will appear from the copending application of Fitzsimmons and Robison, none of relays CLA, CLB and CLC will be energized. Under these conditions, relay RTA will be energized over its second traced pickup circuit including the back point of contact 0 of relay CLA and the back point of contact 0 of relay CLC.

The energizing circuit for relay CLVP will be interrupted at the open back point of contact a of relay RTA. Relay CLVP will accordingly remain deenergized.

As in the previous example, the pickup circuit for relay TC will be open at the open back point of contact b of relay CL4TP and relay TC will remain deenergized.

The pickup circuit for relay RLP, previously traced, will be completed over front contact a of relay l-ZALP and front contact d of relay CL4TP. The previously traced pickup circuit for relay RHP Will be completed over front contact a of relay 12AHP and front contact c of relay CL4TP. Accordingly, both of relays RLP and RHP will be energized.

With contacts a, b and c of relay CLVP open, none of the L relays in panels ICRP through 6CRP will be energized, and these panels will not take part in the subsequent operation.

A circuit now extends from the negative terminal of battery 76 through resistor 88, over back contact d of relay CLVP, the front point of contact b of relay RLP, the front point of contact b of relay RHP, and through the resistive winding of potentiometer M to ground. On the preceding assumptions, the voltage appearing between the wiper and ground will be 9 volts. This voltage is applied over the front point of contact c of relay RLP, the front point of contact d of relay RHP, the back point of contact e of relay CLVP and the back point of contact a of relay TC to output lead 89, and thence to the group retarder leaving speed computer 87. The remaining operation is the same as that previously described, and more fully described in the copending application of Fitzsimmons and Robison, except that the leaving speed V will be calculated in this instance on the basis of an assumed value of curved track rolling resistance of 9 pounds per ton.

In the test compute cycle, track section CL4T is unoccupied. Under these conditions, relays CLVP, RLP and REP will be deenergized, while relay TC will be energized over the back point of contact b of relay CL4TP. For this purpose, resistors and 91 may be so proportioned as to supply any desired voltage to the computer 87, but it will be assumed for purposes of illustration that 25 volts appear across resistor 91, corresponding to a rolling resistance of 25 pounds per ton. This voltage will be applied over the front point of contact a of relay TC and lead 89 to computer 87, which will proceed to check its own operation in the manner de- 17 scribed in the copending application of Fitzsimmons and Robison.

It is believed that the operation of the apparatus of this embodiment of my invention under other conditions will be obvious from the above illustrations and accordingly, no attempt will be made to describe its operation under all possible circumstances.

While I have described only one form of my invention in detail, it will be apparent to those skilled in the art that many changes and modifications are possible within the scope of the invention. Accordingly, I do not wish to be limited to the details of the embodiment shown, but only by the scope of the following claims.

Having thus described my invention, What I claim is:

1. In a classification yard, in combination, a master retarder, a group retarder approached from said master retarder over a stretch of curved track of predetermined length and grade, weighing means located adjacent the entrance end of said master retarder for measuring the axle loading of each cut of one or more cars entering said master retarder, a plurality of Weight repeater relays controlled by said Weighing means and energized in combination in accordance with the axle loading of each cut, means 'for controlling :the master retarder to adjust the leaving speed of each cut to a value in accordance with the energized combination of said relays, a plurality of track sections of predetermined length in said stretch, a plurality of cut-length registering relays, means actuated when the first of said sections is vacated for energizing said cut-length registering relays in a combination in accordance with the number and length of the remaining track sections which are occupied, speed measuring means for producing a voltage output in accordance with the speed of cars approaching said group retarder, a first plurality of potentiometers having a resistive element and wiper, a second plurality of potentiometers having a resistive element and a wiper, means responsive to the approach of a car to said group retarder and controlled by said weight repeater relays and said out length repeater relays for connecting the output of said speed measuring means across the resistive element of one of the potentiometers of said first plurality, means responsive to the approach of a car to said group retarder and controlled by said weight repeater relays and said out length repeater relay for connecting a source of voltage across the resistive element of one of said second plurality of potentiometers, summing means having input terminals and output terminals, means for connecting the wipers of said selected otentiometers and one end of each of said resistive elements across said input terminals, and a utilization device connected across the output terminals of said summing means.

2. A rolling resistance computer, comprising, in combination, a plurality of computer ratio panels, each panel comprising a selecting relay, a weight registration relay, a pair of cut length registration relays, and a plurality of potentiometers each having a resistive element and a wiper adjustable thereon, the potentiometers in a first half of said panels having their wipers adjusted in accordance with a set of Values of a first function of a first variable, weight and cut length, said values each corresponding to a particular energized combination of said registration relays, the potentiometers in the other half of said panels having their wipers adjusted in accordance with a set of values of a second function of said first variable, weight and cut length, said panels being divided into sets comprising one panel from each half, each set having the wipers of its potentiometers adjusted in accordance with a preselected value of said first variable, means for energizing the selecting relay in one set of said panels corresponding to a selected value of said first variable, means for controlling said Weight registration relays in said selected panels over contacts of the energized selecting relays in accordance With the Weight of a cut traversing a stretch of track, means for controlling said out length registration relays in said selected panels over contacts of the energized selecting relays in accordance with the length of said cut, means including contacts of said selected registration relays for applying a fixed voltage across the resistive element of one of said potentiometers in one panel of said selected set, measuring means for producing a voltage in accordance with the speed of a out leaving said stretch, means including contacts of said selected registration relays for applying the voltage from said measuring means across the resistive element of one of said potentiometers in the other panel of said selected set, summing means, and means for applying the voltages developed between the wipers of said selected potentiometers and one end of their resistive elements to said summing means.

References Cited in the file of this patent UNITED STATES PATENTS 2,751,492 Fitzsimmons June 19, 1956 2,819,682 Falkowski Jan. 14, 1958 2,976,401 Berill Mar. 21, 1961 FOREIGN PATENTS 208,415 Australia May 30, 1957 753,069 Great Britain July 18, 1956 811,821 Great Britain Apr. 15, 1959 816,163 Great Britain July 8, 1959 

